1. Field of the Invention
The present invention relates to a driving power source rotational speed control device and a driving power source rotational speed control method, for use in a vehicle that outputs power of a rotary driving power source via a continuously variable transmission as driving power for traveling, that changes the rotational speed of the rotary driving power source in association with changes in the vehicle speed when acceleration is requested.
2. Description of the Related Art
Japanese Patent Application Publication No. 2006-51842 (JP-A-2006-51842) describes a device, used in a vehicle equipped with a continuously variable transmission, that increases the output rotational speed of a rotary driving power source, such as an internal combustion engine, in association with an increase in the vehicle speed when acceleration is requested, in order to obtain sufficient acceleration for a requested output (page 12 and FIGS. 7 to 12). The device of JP-A-2006-51842 corrects an acceleration target input shaft speed (the target output rotational speed of the rotary driving power source) using a vehicle speed change correction amount, so that it increases in association with an increase in the vehicle speed, even if there is no change in the accelerator pedal depression amount.
However, the vehicle may decelerate due to an increase in the travel resistance, such as an increase in the road gradient, even when acceleration is requested. When such deceleration occurs, the target output rotational speed decreases as a result of correction using the vehicle speed change correction amount, because the output rotational speed of the rotary driving power source is changed in association with the vehicle speed as discussed above.
In addition to deceleration due to the travel resistance, reducing the rotary driving power source output rotational speed also makes the driving power insufficient to further decelerate the vehicle. This may make the driver feel uncomfortable.